The instant invention relates to a process to piece in an open-end spinning device in which the feeding of fibers to a collection surface which has been interrupted during the stoppage of the open-end spinning device when the open-end spinning device is switched on again. A yarn end is fed back to the fiber collection surface in synchronization therewith and the fiber feeding to the fiber collection surface, as well as the speed of resumed draw-off of the previously back-fed yarn, is increased to its applicable production value while the fed fibers are incorporated. The instant invention also relates to a device to carry out this process.
It is a known fact that the fiber sliver continues to be combed out by the opener roller after stoppage of fiber feeding (CH-PS 526.646, column 1). Depending on how long the fiber sliver has been stopped before resumption of feeding, different piecing joints result in the yarn.
In order to avoid these disadvantages it has already become known to pivot the fiber tuft out of action range of the opener roller when fiber feeding is interrupted (CH-PS 526.646). This requires, however, a costly design of the feeding device which may lead to malfunctions during the spinning process, while uniform fiber tufts can still not be obtained with certainty, and while damage to the fibers cannot be excluded.
As a remedy it has also been proposed to switch the fiber feeding on and off again before the actual piecing process and to wait for a predetermined period of time before the resumption of fiber feeding (See German Patent No. DE-PS 2,458,042). In addition, the fiber feeding is to be controlled in adaptation to the run-up curve of the spinning rotor. In this manner an always uniform fiber tuft is to be produced in a manner that is always adjustable in the same way in order to improve the quality of the yarn piecing joint and to render it uniform. For this it is, however, necessary to synchronize run-up of the spinning rotor and control of the fiber feeding precisely, as, otherwise, different quantities of fibers remain in the spinning rotor in spite of uniform fiber tufts because of different centrifugal forces in the spinning rotor. The control of fiber feeding in adaptation to the run-up curve of the spinning rotor, furthermore, requires complicated drive and control mechanisms for the fiber feeding. Much time is, furthermore, required for piecing by switching feeding on twice and due to the fact that a predetermined stoppage time must be observed between the switching off and on again.